Analyzer-free hard x-ray interferometry

Objective. To enable practical interferometry-based phase contrast CT using standard incoherent x-ray sources, we propose an imaging system where the analyzer grating is replaced by a high-resolution detector. Since there is no need to perform multiple exposures (with the analyzer grating at different positions) at each scan angle, this scheme is compatible with continuous-rotation CT apparatus, and has the potential to reduce patient radiation dose and patient motion artifacts.Approach. Grating-based x-ray interferometry is a well-studied technique for imaging soft tissues and highly scattering objects embedded in such tissues. In addition to the traditional x-ray absorption-based image, this technique allows reconstruction of the object phase and small-angle scattering information. When using conventional incoherent, polychromatic, hard x-ray tubes as sources, three gratings are usually employed. To sufficiently resolve the pattern generated in these interferometers with contemporary x-ray detectors, an analyzer grating is used, and consequently multiple images need to be acquired for each view angle. This adds complexity to the imaging system, slows image acquisition and thus increases sensitivity to patient motion, and is not dose efficient. By simulating image formation based on wave propagation, and proposing a novel phase retrieval algorithm based on a virtual grating, we assess the potential of a analyzer-grating-free system to overcome these limitations.Main results. We demonstrate that the removal of the analyzer-grating can produce equal image contrast-to-noise ratio at reduced dose (by a factor of 5), without prolonging scan duration.Significance.By demonstrating that an analyzer-free CT system, in conjuction with an efficient phase retrieval algorithm, can overcome the prohibitive dose and workflow penalties associated grating-stepping, an alternative path towards realizing clinical inteferometric CT appears possible.

Mortality not increased in patients with non-functional adrenal adenomas: a matched cohort study

CONTEXT

Mild autonomous cortisol secretion (MACS) is associated with increased mortality in patients with adrenal incidentalomas (AI), but little is known regarding the potential risk associated with non-functional adrenal adenomas (NFAA), which constitute the majority of AI.

OBJECTIVE

Compare mortality risk in patients with NFAA, and different levels of MACS, to matched controls.

METHOD

This was a retrospective matched cohort study. All patients referred to two endocrine centres in southern Sweden because of an AI between 2005 and 2015 were enrolled. Controls (3:1) matched for sex, age, and residency were included. Primary endpoint was all-cause mortality. Outcome data was obtained from the Cause of Death Register. Patients were grouped according to cortisol level post 1-mg dexamethasone suppression test (cortisolDST) (<50 (NFAA), 50-82, 83-137, and ≥138 nmol/L).

RESULTS

1154 patients and 3462 matched controls were included. During a median follow-up of 6.6 years, 210 patients and 505 controls died. There were no statistically significant differences in mortality between patients with NFAA and their controls (HR 1.13 (0.87-1.46)) whereas mortality was increased compared to controls in patients with cortisolDST 83-137 (HR 1.99 (1.38-2.88)) and ≥138 nmol/L (HR 4.09 (2.41-6.93)). Likewise, the mortality risk was increased inpatients younger than 65 years with cortisolDST 50-82 nmol/L compared to controls (HR 2.33 (1.30-4.17)).

CONCLUSION

NFAA does not seem to pose a clinically relevant risk for increased mortality in patients with AI while patients with MACS, and especially younger patients and those with cortisolDST ≥83 nmol/L, have significantly increased mortality risk compared to matched controls.

Detectors for the future of X-ray imaging

In recent decades, developments in detectors for X-ray imaging have improved dose efficiency. This has been accomplished with for example, structured scintillators such as columnar CsI, or with direct detectors where the X rays are converted to electric charge carriers in a semiconductor. Scattered radiation remains a major noise source, and fairly inefficient anti-scatter grids are still a gold standard. Hence, any future development should include improved scatter rejection. In recent years, photon-counting detectors have generated significant interest by several companies as well as academic research groups. This method eliminates electronic noise, which is an advantage in low-dose applications. Moreover, energy-sensitive photon-counting detectors allow for further improvements by optimising the signal-to-quantum-noise ratio, anatomical background subtraction or quantitative analysis of object constituents. This paper reviews state-of-the-art photon-counting detectors, scatter control and their application in diagnostic X-ray medical imaging. In particular, spectral imaging with photon-counting detectors, pitfalls such as charge sharing and high rates and various proposals for mitigation are discussed.

Dissociative recombination study of N3+: Cross section and branching fraction measurements

We report an investigation into the dissociative recombination of the azide radical cation, N(3) (+). The reaction rate constant has been measured to be 6.47 x 10(-7) cm(3) s(-1) at room temperature. This value is smaller than those reported earlier for the ion-electron neutralization of N(3) (+) at nitrogen atmospheric pressure. A strong propensity to dissociate through the N(2)+N channel has been observed.

Detective quantum efficiency dependence on x-ray energy weighting in mammography

An evaluation of the dependence of detective quantum efficiency (DQE) on the incident energy spectrum has been made for mammography. The DQE dependence on the energy spectrum has been evaluated for energy-integrating detectors, photon-counting detectors, and detectors that measure the energy of each photon. To isolate the effect of the x-ray energy spectrum the detector has been assumed to be ideal, i.e., all noise sources are assumed to be zero except for quantum fluctuations. The result shows that the improvement in DQE, if the energy-integrating detector is compared to a single-photon counting detector, is of the order of 10%. Comparing the energy-integrating detector and the detector measuring the energy for each photon the improvement is around 30% using a molybdenum anode spectrum typical in mammography. It is shown that the optimal weight factors to combine the data in the case the energy is measured are very well approximated if the weight factors are proportional to E(-3). Another conclusion is that in calculating the DQE, a detector should be compared to one that uses ideal energy weighting for each photon since this provides the best signal-to-noise ratio. This has generally been neglected in the literature.

[3H]GBR-12935 binding to human cerebral cortex is not to dopamine uptake sites

The binding of the dopamine uptake inhibitor [3H]GBR-12935 to 16 regions of the human brain was investigated in competition experiments with increasing concentrations of GBR-12909, mazindol, and dopamine. The methodology used included a relatively high tissue concentration (8 mg/ml) and addition of 5 mM KCl in the assay buffer. GBR-12909 inhibited 80-90% of the binding in most regions, whereas dopamine only inhibited the binding in the striatum. Mazindol inhibited only part of the cortical binding at concentrations of > 1 microM, whereas the inhibition in the caudate and the putamen also contained a high-affinity component representing the dopamine uptake site. It is concluded that the [3H]GBR-12935 binding sensitive to GBR-12909 cannot be regarded as specific binding to the dopamine uptake site because the displaceable binding most likely is not related to the dopamine uptake site.

Familial amyloidotic polyneuropathy in Sweden: a pedigree analysis

Extended genealogical studies were performed on the heredity patterns in Swedish patients with familial amyloidotic polyneuropathy (FAP) using Swedish historical archives. The population studied included 239 patients: 109 patients were linked to five large pedigrees and 80 patients belonged to 30 smaller pedigrees or nuclear families. In the remaining 50 cases, no genealogical links were found. Differences in mean ages of onset between the different pedigrees were found, although a considerable variation within the pedigrees was also present. There was a tendency for later ages of onset among older generations than younger ones: descendants of affected mothers seem to be more prone to anticipation in age of onset than descendants of affected fathers. Furthermore, there seems to be a tendency for earlier ages of onset among patients with a carrier mother than a carrier father. Some extended pedigrees, from the Skellefteå and Piteå areas, are presented in detail. The former go back into the middle of the 17th century. One important conclusion is that the mutational event may have occurred in late mediaeval times.

Deliberate self-poisoning: treatment follow-up of repeaters and nonrepeaters

Since 1986 psychiatrists and social workers of the Lund Suicide Research Center have investigated subjects admitted to the medical intensive care unit after a suicide attempt. Fifty-nine of 79 deliberate self-poisoners were interviewed 12 months after a suicide attempt. Twenty-one had previously been interviewed 6 months after the index suicide attempt. We obtained minor information on 8 subjects. Two patients had committed suicide. Sixteen subjects (27%) of those who were interviewed showed repeated suicidal behavior (repeaters) during the 1-year follow-up, and their psychiatric diagnoses at the index attempt were most commonly alcohol abuse and dysthymia (DSM-III, Axis I). Compared with nonrepeaters, repeaters had more often made previous suicide attempts, their index attempt was less serious and they were more often in psychiatric treatment at index. At follow-up, repeaters more often than nonrepeaters expressed the need for professional mental health support. Two-thirds of the patients were in treatment at follow-up. About half had remained in continuous treatment and most in psychiatric care for more than 1 year. Repeated self-poisoning occurred despite ongoing treatment. In view of the fact that numerous suicide attempters obviously remain in treatment for several years, we suggest further development and evaluation of long-term treatment strategies.

Characteristics of patients resistant to antihypertensive drug therapy

In order to determine the features that characterize refractory hypertension (RH), patients aged less than 65 years in a hypertension clinic were screened. Thirty-six patients on triple drug therapy with a supine diastolic blood pressure (DBP) of greater than or equal to 5 mmHg above an identified target pressure (90-100 mmHg), or a systolic blood pressure (SBP) greater than or equal to 170 mmHg for the last 6 months (greater than or equal to 3 measurements) underwent a thorough clinical investigation. The frequency of renal artery stenosis (RAS) in the RH patients was 30%. The non-RAS patients had a low occupational status, 76% being either manual workers or unskilled non-manual workers (reference group: 42%; P less than 0.01). They were more obese (body mass index (BMI) 28.8 vs. 25.8; P less than 0.01), and had a longer duration of hypertensive disease. RH patients had a higher prevalence of non-insulin-dependent diabetes mellitus (18 vs. 6%; P less than 0.05), and showed a higher prevalence of nervous complaints and mental distress (44% vs. 12%; P less than 0.001) and musculo-skeletal pain (39% vs. 7%: P less than 0.001). It is suggested that refractory hypertension should be investigated and treated bearing psychosocial factors in mind, concurrently with a screening for secondary hypertension.

Long term experience of felodipine in combination with beta-blockade and diuretics in refractory hypertension

Felodipine, a new dihydropyridine, was given to 58 hypertensive patients in combination with an adrenergic beta-receptor antagonist and a diuretic agent. In all but 2 patients the blood pressure was unsatisfactorily controlled on standard triple therapy, i.e. alpha beta-blocker, a diuretic and a vasodilator. A 48-week follow-up was completed by 54 patients. After an initial dose titration period, the maintenance dose of felodipine was 5 mg twice daily in 14 patients and 10 mg twice daily in 34 patients. In the remaining 6 patients, the dose ranged from 5 mg every morning to 25 mg twice daily. The dosages of beta-blocking agent and diuretic were considerably reduced during the study period. Mean supine blood pressure was reduced from 170/101 mm Hg on triple therapy before felodipine to 145/86 mm Hg (p less than 0.001) after 2 weeks on felodipine. This improvement was sustained throughout the study and was measured at 144/86 mm Hg (p less than 0.001) after 48 weeks. There was no increase in resting heart rate and no orthostatic fall in blood pressure. Bodyweight was not increased and felodipine was generally well tolerated. Three patients were withdrawn owing to side effects and 1 was socially non-compliant. It is concluded that felodipine is a potent and well tolerated vasodilator, and will be useful in the long term combination treatment of previously refractory hypertension.

Effect of quinidine on maintaining sinus rhythm after conversion of atrial fibrillation or flutter. A multicentre study from Stockholm

In a controlled study comprising 176 patients, quinidine in the form of Kinidin Durules was found to reduced significantly the recurrence of the atrial fibrillation during a 1-year follow-up period after successful electric shock conversion. After one year, 51 per cent (52/101) of the patients in the quinidine group, and 28 per cent (21/75) in the control group remained in sinus rhythm (P smaller than 0.001). No less than 43 per cent of the patients converted to sinus rhythm during treatment with maintenance doses of quinidine sulphate before intended DC conversion. Gastrointestinal side-effects were not uncommon, and caused interruption of quinidine treatment in some cases.